JAVA EE: Spring ResourceLoaderAware example | Spring Tutorial | Spring Framework

Wednesday, 29 August 2018

Spring ResourceLoaderAware example | Spring Tutorial | Spring Framework | Spring basics

Master Spring & Java Development!

Subscribe to Ram N Java for clean, beginner-friendly coding guides!

Overview: ResourceLoaderAware in Spring

In the Spring Framework, applications frequently need to load external resources such as text files, XML configurations, or images from the classpath, file system, or web URLs. While Spring's ApplicationContext implements the ResourceLoader interface directly, a bean can obtain a reference to this loader cleanly during its lifecycle by implementing the ResourceLoaderAware interface.

In this guide, you will learn how the ResourceLoaderAware interface works, how Spring injects the ResourceLoader instance, and how to use it to load external resources easily.

Understanding ResourceLoaderAware

The ResourceLoaderAware interface is part of Spring's set of "Aware" callback interfaces:

Lifecycle Callback: When a bean implements ResourceLoaderAware, Spring automatically invokes its setResourceLoader(ResourceLoader resourceLoader) method during bean initialization.
Unified Resource Access: The injected ResourceLoader provides the getResource(location) method, supporting prefixes like classpath:, file:, and standard URLs.
No Direct ApplicationContext Coupling: It grants your bean the ability to load external resources without requiring full access to the broader ApplicationContext.

Step-by-Step Implementation

Implement the Interface: Have your bean class implement org.springframework.context.ResourceLoaderAware.
Override setResourceLoader(): Store the passed ResourceLoader reference in a member field:
public void setResourceLoader(ResourceLoader resourceLoader) { this.resourceLoader = resourceLoader; }
Load Resources: Use the resourceLoader.getResource("classpath:sample.txt") method to retrieve and process files seamlessly.

Recommended Next Videos from Ram N Java

Click here to watch on Youtube:
https://www.youtube.com/watch?v=mi9Imd__Ty4&list=UUhwKlOVR041tngjerWxVccw

Click the below Image to Enlarge:

Spring ResourceLoaderAware example | Spring Tutorial | Spring Framework | Spring basics

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0%20http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.2.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

     <build>

        <plugins>

            <plugin>

                <groupId>org.apache.maven.plugins</groupId>

                <artifactId>maven-compiler-plugin</artifactId>

                <version>3.7.0</version>

                <configuration>

                    <source>1.8</source>

                    <target>1.8</target>

                </configuration>

            </plugin>

        </plugins>

    </build>

</project>

names.txt

Peter

Ram

Juli

ResourceLoaderAwareImpl.java

package com.ram.aware;

import java.io.BufferedReader;

import java.io.FileNotFoundException;

import java.io.FileReader;

import java.io.IOException;

import org.springframework.context.ResourceLoaderAware;

import org.springframework.core.io.Resource;

import org.springframework.core.io.ResourceLoader;

public class ResourceLoaderAwareImpl implements ResourceLoaderAware

{

    private ResourceLoader resourceLoader;

    public void setResourceLoader(ResourceLoader resourceLoader)

    {

        System.out.println(

                "setResourceLoader(ResourceLoader resourceLoader) is called "

                        + "by the Spring Container");

        this.resourceLoader = resourceLoader;

    }

    public void displayFileInfo()

    {

        Resource resource = resourceLoader.getResource("classpath:names.txt");

        try (

                BufferedReader br = new BufferedReader(

                        new FileReader(resource.getFile().getPath())))

        {

            String thisLine = null;

            System.out.println("Names from the files are..");

            while ((thisLine = br.readLine()) != null)

            {

                System.out.println(thisLine);

            }

        }

        catch (FileNotFoundException e)

        {

            e.printStackTrace();

        }

        catch (IOException e)

        {

            e.printStackTrace();

        }

    }

}

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-4.3.xsd">

    <bean id="resourceLoaderAware" class="com.ram.aware.ResourceLoaderAwareImpl" />

</beans>

App.java

package com.ram.core;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.aware.ResourceLoaderAwareImpl;

public class App

{

    public static void main(String[] args)

    {

        ClassPathXmlApplicationContext applicationContext = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        ResourceLoaderAwareImpl resourceLoaderAwareImpl = applicationContext

                .getBean("resourceLoaderAware", ResourceLoaderAwareImpl.class);

        System.out.println("resourceLoaderAwareImpl = "+resourceLoaderAwareImpl);

        resourceLoaderAwareImpl.displayFileInfo();

        applicationContext.close();

    }

}

Output

Aug 13, 2018 9:46:49 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Mon Aug 13 09:46:49 IST 2018]; root of context hierarchy

Aug 13, 2018 9:46:49 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [applicationContext.xml]

setResourceLoader(ResourceLoader resourceLoader) is called by the Spring Container

resourceLoaderAwareImpl = com.ram.aware.ResourceLoaderAwareImpl@5c7fa833

Names from the files are..

Peter

Ram

Juli

Aug 13, 2018 9:46:50 AM org.springframework.context.support.AbstractApplicationContext doClose

INFO: Closing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Mon Aug 13 09:46:49 IST 2018]; root of context hierarchy